Constriction type vacuum interrupter

ABSTRACT

A vacuum interrupter is provided in which the arc produced in moving opposed contacts to open position is confined within constricting walls. The constricting walls are disposed adjacent to a set of ring contacts and operate to reduce sideway motion of the arc column so that the arc can move only along the ring contacts thereby reducing the arc energy that is released in a given volume and provide rapid heat exchange with the atmosphere thereby increasing the interrupting limit of the interrupter.

I United States Patent 1191 1111 3,849,617 Pflanz Nov. 19, 1974 [5 CONSTRICTION TYPE VACUUM 1,901,067 10/1969 Germany zoo/144 B INTERRUPTER 1,196,121 6/1970 Great Britain 200/144 B [75] Inventor: aearslsiert M. Pflanz, Westwood, Primary Examiner Robert S- Macon Attorney, Agent, or Firm-Robert C. Jones [73] Assignee: Allis-Chalmers Corporation, Milwaukee, [22] Filed: 1972 A vacuum interrupter is provided in which the are 211 App], 300,725 produced in moving opposed contacts to open position is confined within constricting walls. The constricting walls are disposed adjacent to a set of ring U.S-

B t t d p t t reduce id y ti f th [51] hit. Cl. H0111 33/66 arc column so h the arc can move only along the [58] Fleld of Search 200/144 B ring Contacts thereby reducing the are energy that is released in a given volume and provide rapid heat ex- [56] References Cited change with the atmosphere thereby increasing the in- FOREIGN PATENTS OR APPLICATIONS terrupting limit of the interrupter. 1,391,515 l/l965 France 200/144 B 1,511,782 12/1967 France 200/144 B 28 Chums 8 Draw F'gures CONSTRICTION TYPE VACUUM INTERRUP'IER BACKGROUND OF THE INVENTION The high current are in a vacuum interrupter shows essentially the same characteristics as a high pressure are burning, for example, in air. One of the properties which characterizes such an arc is the low arc voltage which can be shown to indicate a gaseous atmosphere in esssential thermal equilibrium. In this case, the arc voltage is a function of the heat transfer properties to walls surrounding the conductive path of the arc. In a vacuum interrupter, the mechanisms of heat transfer from the arc to surrounding walls are by radiation, diffusion and transport of ionization energy in the diffusion process. In conventional vacuum interrupters, the walls surrounding the are are in the form of shields which are spaced relatively far from the arc column thus reducing the effectiveness of the heat transfer by diffusion and transport of ionization energy.

Another characteristic of a high current are in a vacuum interrupter with a conventional arc movement type of contact structure is the violent looping and rotation of what appears to be a concentrated arc column.

SUMMARY OF THE INVENTION In accordance with a preferred embodiment of the present invention, there is provided an interrupter in which the shield structure, which herein is more accurately referred to as a constrictor structure, hugs the arc in a relatively closely spaced relationship. This closely spaced relationship of the constricting walls relative to the arc does not affect the amount of heat transferred by radiation. However, the diffusion process is much more effective, because of the proximity of the cold constricting walls to the arc column which causes an increase of the absolute value of the density gradient of the vapor arc atmosphere which, with a given diffusion coefficient, results in an increased mass diffusion. Since the structure provided increases the efficiency of heat transfer, the deionization at current zero, is increased and, therefore, a faster build-up of dielectric strength across the arc gap is obtained.

Accordingly, the general object of the invention is to provide an improved vacuum interrupter which provides control over a high current arc.

Another object of the invention is to provide an improved vacuum interrupter in which the heat transfer characteristics is improved to more effectively deionize the arching gap at current zero at which interruption is to occur.

Yet another object of the invention is to provide an improved vacuum interrupter having means to control the violent irregular movement of the high current are column and thereby control the are energy.

Still another object of the invention is to provide an improved vacuum interrupter which includes means for enhancing the arc movement over the electrodes and thereby reduce erosion of the electrodes.

A further object of the invention is to provide an improved vacuum interrupter having an effective shield area which is less than the area of shields provided in presently known interrupters.

A still further object of the invention isto provide an improved vacuum interrupter having a shield with'a high heat absorbing capacity.

Another object of the invention is to provide an improved vacuum interrupter having a shield means which permits heat exchange by direct cooling to the atmosphere surrounding the interrupter.

A still further object of the invention is to provide an improvided vacuum interrupter in which the self magnetic field of an arc movement structure is enhanced by an externally applied magnetic field which operates to increase the arc speed on the arc runner structure.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a view partly in vertical section and partly in elevation of the improved vacuum interrupter of the invention;

FIG. 2 is a fragmentary view similar to FIG. 1 showing the ring contacts in an intermediate position between open and closed positions;

FIG. 3 is a sectional view through the interrupter taken in a plane represented by the lines Ill-Ill in FIG.

FIG. 4 is a sectional view through the interrupter taken in a plane represented by the line IV-IV in FIG.

FIG. 5 is a view of a modification of the interrupter shown in FIG. I which incorporates magnetic structure;

FIG. 6 is a partial view of a modification of the interrupter shown in FIG. 1, embodying the principles of the invention;

FIG. 7 is a partial view of another modified form of the interrupter shown in FIG. 1, embodying the principles of the invention; and,

FIG. 8 is still another modification of an interrupter embodying the invention.

DESCRIPTION OF THE INVENTION Referring to the drawings, the reference numeral 10 designates generally a vacuum circuit interrupter in which thenovel characteristics of the invention have been incorporated. The interrupter 10 includes an inner circular wall member 11 having an axial bore 12. Spaced from and surrounding the inner wall member 11 is a circular outer wall member 14 which is formed with a relative smooth exterior peripheral surface 16. In the preferred embodiment, both the inner and outer wall members 11 and 14, respectively, are formed of a metallic material such as copper. However, it is to be understood that the members 11 and 14 can be formed of a material other than metallic such as ceramic or glass if preferred. A pair of circular metallic end caps 17 and 18 having axial openings 21 and 22, respectively, are secured to the respective opposite axial ends of the inner and outer wall members in vacuum tight relationship as by being brased thereto. The end caps 17 and 18 serve to maintain the inner and outer wall members 11 and 14 in coaxial spaced relationship and also to seal the circular space 23 between the wall members to provide an area in which a high vacuum is maintained. Evacuation of the space 23 is accomplished by means of an evacuating process, which is well known in the art, through a tubulation 24 that is disposed in a suitable opening 26 formed in the member 14 with the tubulation 24 being brazed therein. With the space 23 evacuated to the extent desired, the tubulation 24 is sealed.

Located within the evacuated envelope of the interrupters I0 is a pair of separable contact rods 26- and 27,

shown in FIG. 1 in their open position. As shown in FIGS. 1 and 2, the contact rod 26 constitutes the relatively movable member which extends freely through the axial bore 28 of an insulator 28. The insulator 29 is constructed and arranged to extend through an opening 31 formed in the end cap 18 into the evacuated space 23 midway between the wall members 11 and 14. A vacuum tight seal between the abutting weather skirt of the insulator and the opening 31 through which the insulator passes is affected by brazing, for example.

Axial movement of the contact rod 26 to contact closed or to a contact open position while still maintaining a vacuum tight sealed relationship of the contact rod 26 and the evacuated space 23 is accomplished by means of a flexible bellows 32. The bellows 32 surrounds the contact rod 26 and has one end brazed to the outer peripheral surface of the insulator 29. At its opposite end the bellows are sealed to the contact rod as by being brazed thereto.

The contact rod 27 constitutes the relatively fixed member which is arranged to extend freely through an axial bore 41 of an insulator 42. The insulator 42 extends through a suitable opening 43 formed in the end cap 17 and into the evacuated space 23 in axial alignment with the contact rod 26. As indicated, a vacuum tight seal is effected between the insulator 42 and opening 43 by brazing. The outer end of the insulator 42 is fitted with a circular metal cap 44 that is brazed to the insulator and to the rod 27.

To effect rapid movement of the arc column which is developed when the contact rods 26 and 27 are moved to contact open position, a pair of ring contacts 46 and 47 are provided. The ring contacts 46 and 47 are identical and are constructed in the form of incomplete toroids, as shown in FIGS. 3 and 4, each having ends 46A and 46B, and 47A and 47B, respectively. Each of the ring contacts 46 and 47 are supported in spaced relationship to each other and also in concentn'c relationship within the evacuated space 23.

To this end, a pair of support insulator rods or pins 51 and 52 are provided, FIGS. 1 and 4, which are identical in construction and arrangement. Thus, a description of the pin 51 will also apply to the pin 52. As shown in FIGS. 1 and 4, the insulator pin 51 is formed with a blind bore 53 and is secured to the inner surface of the end cap 18 as by being brazed thereto. A screw 54 which passes through a suitable opening provided in the blind end of the pin bore 53 is threadedly engaged in the ring contact 46 to secure the ring contact to the pm.

To protect and prevent arc particles from striking and accumulating on the surface of the pin 51, there is provided a shield 56. As shown, the shield 56 is in the form of a truncated cone which is arranged to surround the pin 51. The smaller diameter end of the shield 56 adjacent to the ring contact 46 is brazed thereto to secure it in operative position. The opposite end of the shield 56 adjacent to the end cap 18 is of a diameter which is sufficiently large enough such that metal vapor emanating from the arc B and rebounding at least once from the constrictor walls 11 and 14 will be intercepted by shield 56 and cannot therefore contaminate the insulating surfaces of pins 51 and 52.

The other pin 52, shown in FIG. 4, which is similar in all respects to the pin 51, is also secured to the inner surface of the end cap 18 and extends upwardly therefrom. The upper end of pin 52 is secured to the end 46A of the ring contact 46 by means of a screw 54A. Protection from are particles is likewise afforded to the pin 52 by means of a truncated shield 56A which is constructed and mounted about the pin 52 in the same manner as shield 56 is associated with the support pin 51. The opposite end 468 of the ring contact 46 is secured to the inner extending end of the movable contact rod 26, as being brazed thereto. Thus, the ring contact 46 is concentrically supported within the evacuated space 23 by the support pins 51 and S2 and by the contact rod 26.

In a similar manner the ring contact 47 is supported in spaced relationship to the ring contact 46 and also in concentric relationship between the wall members 11 and 14 in the space 23. To this end, a pair of support pins 61 and 62 shown in FIGS. 1 and 3, are provided. The pins 61 and 62 are identical in construction and arrangement to the pins 51 and 52. Thus, the one pin 61 is secured to the inner surface of the end cap 17 and is secured to the ring contact 47 by means of a screw 63. A truncated shield 64 surrounds the pin 61 and serves to intercept any of the arc particles that may be impelled towards the pin 61. The other pin 62 is similarly disposed and is secured to the end 47A of the ring contact 47 by means of a screw 66. A truncated shield 67 surrounds the pin 62 and operates in the manner and for the purpose as the shield 64 serves. The opposite end 4713 of the ring contact 47 is brazed to the inner extending end of the stationary contact rod 27. Thus, the ring contact 47 is supported in spaced relationship to the ring contact 46 and in concentric relationship within the space 23 by the pair of pins 61 and 62 and by the stationary contact 27.

With the ring contact 46 supported as described there is sufficient flexibility in that portion 48, FIG. 4, of the ring contact 46 which is between the end 468 and the pin 51 to allow the portion 48 to deflect upwardly into engagement with the ring contact 47. Thus, inward movement of the contact rod 26 will cause the associated portion 48 of the ring contact 46 to deflect upward into contact closed position with the ring contact 47. The adjacent surfaces of the ring contacts 46 and 47 that are adapted to engage are provided with contact tips or pads 68 and 69, respectively, which have antiwelding properties and are brazed to opposed surfaces of the associated n'ng contacts. Thus, actuation of the movable contact rod 26 inwardly or upwardly as viewed in FIG. 1, will operate to deflect the end 4613 of the ring contact 46 upwardly to a contact closed position wherein the associated contact tip 68 is in electrical engagement with the contact tip 69 of the ring contact 47.

conversely, axial movement of the contact rod 26 outwardly or downwardly, as viewed in FIG. 1, will move the end 468 of the ring contact 46 away from the end 47B of the opposed ring contact 47 to contact open position. When the movable ring contact 46 separates from the stationary ring contact 47 an arc is drawn between the respective contact tips 68 and 69. As the movable end 463 of the ring contact 46 is moved progressively away from the stationary ring contact 47 the spacing between the tips 68 and 69 of the ring contacts 46 and 47, respectively, becomes progressively larger and larger. As a result, the are A, FIG. 2, initially drawn upon the initial separation of the contacts develops into a longer are moving radially between and around the ring contacts 46 and 47. Thus, as the arc moves radially around the ring contacts 46 and 47 between the adjacent surfaces thereof the length of the arc increases to a maximum length equal to the spacing between the ring contacts when the ring contacts are in parallel spaced relationship as depicted by the arc B in FIG. 1. The magnetic effect of the arc and of the ring contacts 46 and 47 will impel the arc circularly around the ring contacts. The speed at which the arcs move circularly on the ring contacts depends upon the magnitude of the arcing current and varies as a function thereof. Thus, arcs of relatively low current magnitude move at considerably less speed than arcs of high current magnitude. the arc developed at initial separation of the ring contact tips 68 and 69 moves circularly around the contact rings till a natural current zero is reached, at which interruption can take place. Interruption is successful if the residual arc column can be deionized faster than the circuit recovery. deionization depends on the rate of energy input into the arc and the extraction of are energy per unit time by heat transfer.

The interrupting limit of the interrupter of the present invention can be increased by preventing sideway motion of the arc column transverse to the longitudinal direction of the ring contacts 46 and 47. This is true because when sidewise looping of the arc is prevented or eliminated, the arc length and thus the arc energy is reduced. Moreover, since the arc will move along the ring contacts, the are energy released per unit volume is reduced. As shown, the arc column between the ring contacts 46 and 47 moves generally in the Amperian direction under the influence of the self magnetic field in the ring contact structure. Occasionally, retrograde motion and reignition on sections of the ring contacts, over which the arc has moved before, are experienced. This retrograde motion is more often experienced with low current vacuum arcs. The high current arc in a vacuum interrupter being essentially a high pressure are is generally not subject to retrograde motion. It is, thus, highly desirable to increase the motion of the arc over the ring contacts which reduces reignition and reduces contact erosion because the residence time of the arc terminals on any section of the ring contacts is reduced. With a reduction in contact erosion effected, less contamination of the arc gap is obtained and as a result, an increase in the interrupting limit of the interrupter is possible.

The aforementioned desirable characteristics in an interrupter are obtained in the present invention by providing arc constrictor means adjacent to the ring contacts 46 and 47. The increase in the interrupting limit, that is the short time loading above the rated limitation of the interrupter, depends on the particular exemplifying interrupter structure, on the ability of the wall surfaces of the constrictor walls to withstand a permissible maximum temperature to maintain a high temperature gradient for rapid cooling and deionization of the arc gap at current zero.

In providing the constrictor walls for the ring contacts a design is required which considers the criterion that exposed surface of the constrictor wall shall not absorb more than approximately 100 KW per square inch of exposed surface and also the criterion of exposed time of the constrictor walls to heat input along with the cooling rate to the ambient on duty cycle switching of the interrupter.

In the constrictor provided, it is required that it never exceed in single or duty cycle operations a temperature equal to 1/100 of the center temperature ratios of the high current arc in a vacuum interrupter. Typically, the center temperature of an arc is greater than 4.0()0 K. This constrictor temperature is computed on the assumption that the entire arc energy released on one or more interruptions is transferred to the constrictor volume.

The arc energy is to include all arcing events within any time interval of five times Tth, where 'lth the thermal time constant of the constrictor. The reason for this criterion is to maintain an adequate average particle density gradient in a radial direction, which permits sufficiently rapid deionization of the arc gap for successful interruption.

In the structure disclosed, the high current arc moves along the ring contacts 46 and 47 with a velocity of the order of at least 50 meters per second for currents in excess of 5 M. With the present constrictor, the wall surfaces thereof, opposite to the arc, are subjected to energy absorption at a lineal rate of 5 meters per second, the constrictor or shield can be exposed to a much higher power input than heretofore possible. Thus, since the constrictor can be exposed to a higher power input for a given volume, this, conversely, results in reduced constrictor area for a given interrupter rating. As a result, a more compact vacuum interrupter for a given rating can be manufactured. Moreover, since the constrictor of the present invention is arranged on both sides along the ring contacts 46 and 47, a still further reduction in the size of the interrupter can be made without reducing the rating capabilities of the interrupter.

In FIG. 1, the constrictor includes the outer circular member 14 and the coaxial radially spaced inner member 11. As shown, the inner surface of the outer members 14 and inner surface of the inner member 11 are formed in a manner so that in cross-section, they present an hour glass configuration having open ended upper and lower communicating chambers 71 and 72.

The hour glass configuration of the constrictor 70 provides an effective shield area which in a preferred format is the entire area opposite the length of the ring contacts over which the arc passes and extending approximately one centimeter in either direction of the arc length between the ring contacts.

Thus, as depicted in FIGS. 1 and 2, an are as exemplified by the arc B as it moves between the ring contacts 46 and 47 over the length thereof is confined by the restricting wall; surfaces of the constrictor 70 from sidewise looping. Thus, any tendency of the arc tenninals on the ring contacts 46 and 47 to loop upwardly and downwardly on the surfaces of the ring contacts will be inhibited.

From the foregoing description of the improved interrupter set forth, the novel structure pennits addition of mass to the constrictor or shield structure so as to increase the heat absorbing capacity of the constrictor. Since the constrictor is exposed externally to atmosphere, a greatly improved cooling of the constrictor shield is obtained resulting in an increase in the duty cycle switching ability.

In FIG. 5, a modification of the interrupter of FIG. 1 is disclosed. In the modified structure parts similar to those of the interrupter of FIG. 1 are given the same identifying reference numbers. As shown in FIG. 5, the interrupter 80 includes the inner and outer members 11 and 14- as well as the top and bottom end caps 17 and 18. Ring contacts 46 and 47 are supported in coaxial relationship within the evacuated space 23 by the shielded insulated pins 51 and 52 and 61 and 62 and the stationary and movable contact rods 26 and 27.

Suspended within the hollow circular core 81 of the inner member 11 is a pair of magnet structures 82 and 83. The magnet structures 82 and 83 are disposed within the core 81 so that the North pole of each of the structures 82 and 83 are adjacent but spaced from each other. With the addition of the magnet structures 82 and 83 the arc is crossed by a magnetic field and the force acting on the arc will be determined by the vector product of the arc current and the flux density. Thus, the magnetic field produced by the magnetic structures 82 and 83 will operate to produce a radial magnetic field which aids the force acting on the are which is produced by the field of the ring contacts.

The magnetic structures 82 and 83 may be in the form of magnetic coils which are connected in the interrupter circuit for energization. However, the magnetic structures 82 and 83 can also be permanent magnets if desired.

In FIG. 6, another modification of a constrictor type interrupter is disclosed. In FIG. 6, a partial showing of a symmetrical circular interrupter similar to the interrupter depicted in FIG. 1 is made. As shown, the interrupter 90 includes an outer circular member 91 and an inner circular member 92 which is coaxially disposed within the outer member 91. A pair of circular end cap plates 93 and 94 are sealed to the opposite axial ends of the inner and outer members 91 and 92 in vacuum tight relationship. The usual tubulation (not shown) for effecting the evacuation of the space 95 between the outer and inner members 91 and 92 is provided. A pair of incomplete toroidal ring contacts 96 and 97, similar to the ring contacts 46 and 47, are supported in coaxial spaced relationship to each other and to the outer and inner members 91 and 92 in the evacuated space 95 in the same manner as the ring contacts 46 and 47 are supported in the interrupter of FIG. 1. Thus, the ring contact 96 is supported by a pair of shield protected insulator pins 98, one of which is shown, to which the incomplete toroidal ring contact 96 is secured at a point approximately midway between its ends. The other of the pins 98 (not shown) receives one end of the ring contact while the opposite end thereof is secured to the fixed contact rod (not shown). In a similar manner, the incomplete toroidal ring contact 97 approximately midway between its ends is secured to one of a pair of insulator pins 99 while the other of the pins 99 (not shown) fixedly support one end of the ring contact 97. The opposite end of the ring contact 97 is secured to the movable contact rod (not shown).

In the interrupter of FIG. 6, a constrictor 101 is provided which operates to prevent the sidewise looping of an arc as it moves around the ring contacts 96 and 97. As shown, the constrictor 101 is formed of a plurality of coaxially arranged spaced apart inner and outer sets of metallic discs 102 and 103, respectively. The inner set of discs 102 include a pair of lower discs 102A and 1028; a pair of upper discs 102C and 102D; and a pair of intermediate restrictor discs 102E and 102F. The discs 102A, B, C and D are of the same diameter and are provided with an axial bore 105 of a diameter sufficiently large enough to permit the discs to be disposed about the inner circular member 92 and to be electrically isolated from it as shown. In like manner, the restrictor discs 102E and F are also provided with an axial bore so they also may be disposed about the inner member 92. However, the diameters of the restrictor discs 102E and F are larger than the diameters of the upper and lower discs.

The outer set of discs 103 include a plurality of lower and upper discs 103A, 1038, 103C and 103D which are coaxial with and in the same horizontal planes as the associated discs 102A. B, C and D. The discs 103A. B, C and D are of a diameter to fit within the interior of the outer envelope member 91 without having contact therewith. The axial bores of the discs 103A, B, C and D are such that the inner surfaces of the bores are spaced from the adjacent ring contacts 96 and 97 the same distances as the outer periphery of the complementary discs 102A, B, C and D are spaced from the ring contacts. The outer set of discs 103 also includes a pair of restrictor discs 103E and F each having an axial bore such that the inner peripheral surface of the discs are spaced the same distances from the ring contacts as the outer peripheral surface of the restrictor discs 102E and F are spaced from the ring contacts.

For maintaining the inner set of discs 102 in operative position within the evacuated space 95, there is provided a plurality of rods 104, one of which is shown, which are symmetrically arranged in equispaced rela tionship to each other on a circle whose center coincides with the axis of the interrupter. The rods 104, one of which is shown extends through suitable aligned openings formed in the discs 102 and are secured to the upper and lower end cap members 93 and 94. Axial spacing of the discs 102 is obtained by operation of insulator spacers 106 which are disposed on the rods 104 and located between each of the discs. Spacing of the assembled set of discs 102 is accomplished by means of lower and upper ceramic spacer tubes 107 and 108 which are mounted on the lower and upper ends of the rods 104. The tubes 107 and 108 operate to maintain the assembled inner set of discs in operative position relative to the ring contacts 96 and 97.

A similar arrangement is provided for maintaining the outer set of discs 103 in assembled operative position. To this end, a plurality of rods 111, one of which is shown, are symmetrically arranged in equispaced relationship about an axis which also coincides with axis of the interrupter. The rods 111 are likewise secured to the top and bottom end caps 93 and 94. Ceramic spacers 112 disposed on the rods 11 serve to maintain the individual discs 103 in axial spaced relationship to each other. A pair of ceramic insulator tubes 114 and 115 are mounted on the upper and lower ends of each of the rods 11] and operate to maintain the outer set of assembled discs 103 in operative position relative to the ring contacts 96 and 97.

The interrupter operates similar to the manner in which the interrupter 10 of FIG. 1 operates. That is, the movable contact rod (not shown) associated with the interrupter 90 moves the deflectable end of the ring contact 97 out of engagement with the ring contact 96 to open position. The arc initiated on the contact pads or tips (not shown) will move around the ring contacts. The arc in moving around the ring contacts is restricted from sidewise looping by the constrictor 101 by operation of the restricting discs 102E and F and 103E and F which cooperate and serve to repress the centeral portion of the arc to a greater extent than do the upper and lower sets of discs 102C and D and 103C and D and 102A and B and 103A and B.

In FIG. 7, a further modification of the invention is shown in which an interrupter 110 is provided with a constrictor 115. The interrupter 110 is similar to the interrupter 90 of FIG. 6, the modification being effected in the constrictor discs thereof. As shown in FIG. 7, the inner set of constrictor discs 116 includes a plurality of restrictors 116. These discs have an enlarged axial opening that provides an inner edge surface which is disposed adjacent to spaced ring contacts 117 and 118. The upper ring contact 117 is supported within the evacuated space 119 by a plurality of shielded insulator rods 121, one of which is shown, and the fixed contact rod (not shown). The lower deflectable ring contact 118 is supported by a plurality of shielded insulator rods 122, one of which is shown, and the movable contact rod (not shown) in the manner similar to the supporting arrangement shown and described for the ring contacts 46 and 47 in FIG. 1.

The constrictor 115 also includes a set of lower discs 116A and 1168 and a set of upper discs 116C and 116D. The discs 116A, B, C and D each have a smaller outside diameter than the outside diameter of the discs 116E and 116F. Thus, with the discs 116 of the constrictor mounted in operative positions, the outer surfaces of the restrictor discs 116E and F will be disposed as close as feasible to the central portion of an are drawn between the ring contact 117 and 118. Since the outside diameter of the discs 116A, B, C and D is smaller than the diameter of the outside diameter of the restrictor discs 116E and F, the outer surfaces of the upper and lower set of discs will be spaced from the ring contacts 117 and 1 18, respectively, a distance substantially the same as the spacing that exists between the restrictor discs 116E and F and the ring contacts.

The constrictor 115 also includes an outer set of discs 123 including a plurality of restrictor discs 123E and F which have an axial opening smaller than the inside diameter of the discs 123A, B, C and D. Thus, the inner periphery of the restrictor discs 123E and F in cooperation with outer periphery of the discs 116E and F will operate to repress the central portion of an are moving around the ring contacts 117 and 118 to prohibit sidewise looping of the arc. The upper and lower discs 123A, B, C and D complement the associated outer discs and complete the constrictor 115. Thus, with the arrangement provided the cross-sectional hour glass configuration is preserved.

The discs 116 and 123 are all formed with a circular depression. Thus, when the discs are mounted in spaced stacked relationship, as shown, the axial projecting surfaces occasioned by the circular depression in each disc cooperate with the adjacent projecting surfaces of adjacent discs to define labyrinth passages that provide condensing surfaces for arc products which move in a line-of-sight path of travel.

To support and secure the discs 116 in operative position within the interrupter 110, a plurality of spaced openings are formed in each disc (one of which is shown) and are aligned with the corresponding openings formed in adjacent disc. An insulator rod 126 is inserted into the axial aligned openings, with the rod 126 being secured to the end caps. The rods 126 operate to maintain the discs 116 in an operative position with respect to the axis of the interrupter. For spacing the discs 116 axially from each other insulating washers 127 are mounted on the rods 126 and are disposed between each of the discs 116. The assembled constrictor discs are maintained in operative position adjacent the ring contacts 117 and 118 by means of an upper and lower insulated spacer 128 and 129 which are disposed on the ends of the rods. The stack of discs 116 is also spaced so as to be maintained electrically isolated from the wall 92 by making the inside diameter of discs 116 larger than the outside diameter of the wall 92.

A similar arrangement is provided for the discs 123. Thus, a plurality of circularly spaced insulator rods 131 (one of which is shown) are inserted through aligned openings formed in the discs 123. The rods 131 are secured to the end caps and operate to maintain the discs in operative position in the interrupter. Insulating washers 133 mounted on the rods 131 and interposed between each of adjacent discs 123 operate to maintain the discs 123 in axially spaced relationship. The entire assembly of constrictor discs 123 is maintained in operative position adjacent the ring contacts 117 and 118 by means of insulator spacers 134 and 136 which are mounted on the ends of the rods 131.

In FIG. 8, a still further modification of a constrictor type vacuum interrupter is disclosed. The interrupter of FIG. 8 is generally identified by the reference number 140 and includes an envelope 141 having a hollow cylindrical electric insulator housing 142 and metallic axial end caps 143 and 144. End caps 143 and 144 are joined in vacuum tight relationship to the insulator housing 142 by cylindrical flanged rings 146 and 147 as by being welded to the outwardly extending radial flange of the rings. The rings 146 and 147 are suitably secured in a sealed relationship to axial ends of the housing 142.

A metallic contact rod 148 extends through the end cap 143 into the interior of the envelope and is insulated from the end cap by means of an insulator sleeve 149. The insulator sleeve 149 extends through a suitable opening in the end cap 143 and is sealed therein. The diameter of the bore of the insulator 149 is larger than the diameter of the contact rod 148 to provide an insulating spacing therebetween. A sealing sleeve encompasses the rod 148 and is brazed thereto to provide a vacuum tight seal therewith. The lower end of the sealing sleeve encompasses the upper axial end of the insulator 149 and is sealed thereto.

A lower movable contact rod 156 extends through the axial bore of an insulator 157 which is disposed in sealed engagement in a suitable opening provided in the end cap 144. The diameter of the bore of the insulator 157 is larger than the diameter of the movable contact rod 156 thereby providing insulating spacing between the two. A flexible cylindrical bellows 158 is secured in a vaccum tight connection to the outer axial end of the insulator 157. The other end of the bellows 158 surrounds and is secured in a vacuum tight connection to the contact rod 156.

A pair of ring contacts 161 and 162 in the fonn of incomplete toroids, which are similar to the ring contacts 46 and 47 of the interrupter 10, are supported in spaced relationship to each other and in concentric relationship within the envelope 141. As shown in FIG. 8, a plurality of support brackets 163, one being shown,

are provided to support the ring contact 161. The bracket 163 is secured to the inner surface of the top end cap 143 and depends therefrom with the lower end receiving the ring contact 161 as being brazed or otherwise secured therewith. The other of the brackets 163 is likewise secured in depending relationship to the end cap 143 with its depending end being secured as by being brazed thereto to a free end of the ring contact 161. The opposite end of the ring contact 161 is secured to the inner end of the contact rod 148. Thus, the ring contact is supported at three equispaced points. to maintain the ring contact in axial fixed position within the envelope 141. The lower ring contact 162 is likewise provided with three point support, with the arrangement being similar to that described with respect to the ring contact 46 of the interrupter in FIG. 1. To this end, the ring contact 162 at approximately midway between its ends is secured to the end of a bracket 166 with the lower end of the bracket being brazed or otherwise secured to the end cap 144. Another bracket (not shown) similar to bracket 166 securely supports a free end of the ring contact 162. The oppposite end of the ring contact is brazed or otherwise secured to the inner end of the movable contact rod 156. Thus, the ring contact 162 is likewise supported in spaced parallel coaxial relationship to the ring contact 161. However, that portion of the ring contact 162 between the fixed bracket 166 and the movable contact rod 156 is sufficiently flexible to permit deflection of the end of the ring contact 162 that is secured to the movable contact rod 156, upwardly to a contact closed position in engagement with the end of the ring contact 161. This movement of the ring contact 162 is accomplished by axial movement of the contact rod 156. Adjacent facing inner surfaces of the ring contact 161 and 162 are provided with contact tips or pads 168 and 169, respectively, of suitable contact material, such as a compound with antisticking or antiwelding properties, as is well known.

The interrupter 140 includes a constrictor means 170 having an outer member 171 and an inner member 172. The inner member 172 is preferably a single cylindrical metallic body having an axial bore 173. A plurality of relatively deep grooves 174 is formed in the peripheral surface of the member 172 to form a plurality of equispaced parallel horizontally outwardly extending discs 175A, B, C, D, E and F. The constrictor inner member 172 is supported within the interrupter envelope 141 in coaxial relationship therewith and substantially equidistant between the end caps 143 and 144. To this end, a pair of insulators 176 and 177 having peripheral skirts are provided. The insulator 176 is fixedly bonded to the inner surface of the upper end cap 143 and extends downwardly so that an axial hub portion 178 thereof engages in an axial counterbore 179 forward in the member 172. A tubular shield 181 which is secured to the end cap 143 is disposed around the insulator 176 and extends downwardly to a point short of the axial end face of the inner member 172. The shield 181 serves to intercept metallic arc particles thereby preventing such particles from striking and adhering to the insulator 176.

The lower insulator is similarly arranged being fixedly bonded to the inner surface of the lower end cap 144. An axially extending hub portion 182 of the 6 insulator 177 engages within an axial counterbore 183 forward in the inner member 172. Thus, the inner member 172 is fixedly secured in a coaxial intermediate position within the envelope 141 with the peripheral edges of the discs 175 adjacent to but spaced from the ring contacts 161 and 162. A tubular shield 186 is disposed about the insulator 177 and is secured to the end cap 144 and extending therefrom to a point short of the inner member 172.

The constrictor also includes an outer member 171 which is preferably a single cylindrical hollow metallic body having a plurality of grooves 192 formed in its inner peripheral wall surface. The grooves 192 operate to form equally spaced apart parallel inwardly extending horizontal discs 193A, B, C, D E and F. The discs 193 are complementary to the discs 175. To support the outer member 171 in operative position relative to the ring contacts 161 and 162, a pair of spiders 196 and 197 are provided. The upper spider member 196 is secured to the axial end face of the inner member 172 as being brazed thereto. The spider 196 is formed with a plurality of radial outwardly extending fingers of which two 196A and 196B are shown. The spider fingers extend over the outer member 171 and are securely attached to the member as by being brazed thereto. A similar spider 197 is secured to the lower axial end face of the inner member 172. The spider 197 is also formed with a plurality of radial outwardly extending fingers of which two 197A and 197B are shown. The fingers of the spider 197 extend under the outer member 171 and are securely attached thereto. Thus, the inner member is securely supported in operative position within the ring contacts 161 and 162 with the restrictor discs thereof spaced adjacent to the ring contacts. On the other hand, the outer constrictor member 171 is securely supported in operative position outwardly of the ring contacts by the spider members 196 and 197 with the restrictor discs 193 thereof spaced adjacent to the ring contacts.

It is apparent that an are moving around the ring contacts 161 and 162 is efiectively prevented from sidewise looping by operation of the repression effect provided by the restrictor discs 175 and 193. Also, the single structures of the inner and outer members 171 and 172 provides for rapid heat transfer from the arc gap thereby providing very efiective deionization of the arcing gap around current zero. As a result, a highly improved vacuum interrupter has been conceived which has a greatly improved duty cycle switching ability.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a vacuum circuit interrupter;

an evacuated housing;

a pair of ring contacts in the form of incomplete toroids supported within said housing;

a pair of relatively movable contact rods extending into said housing with each contact rod being connected to an end of an associated ring contact; and,

restricting means supported in insulated relationship within said housing and operable on an are moving between said ring contacts to effect lateral repression of an arc to prevent sidewise looping of the are.

2. A vacuum circuit interrupter according to claim 1 wherein said restricting means operates from both sides of said ring contacts on an are moving between said ring contacts.

3. A vacuum circuit interrupter according to claim 2 wherein said restricting means also serves as a shield to intercept metallic arc particles which are developed when an arc is drawn between said ring contacts.

4. A vacuum circuit interrupter according to claim 3 wherein said ring contacts are supported in spaced parallel relationship and one end of one of said ring contacts is deflectable into and out of engagement with adjacent end of the other of said ring contacts.

5. A vacuum circuit interrupter according to claim 4 wherein said shield presents a shield area opposite the length of said ring contacts over which the arc passes and extending approximately one centimeter in either direction of the arc length between said ring contacts.

6. A vacuum circuit interrupter according to claim 1 wherein there is provided means for enhancing the self magnetic field of an are moving around said ring contacts to thereby increase the speed of the are along said ring contacts.

7. In a vacuum circuit interrupter; a first circular member; a second circular member surrounding said first circular member in radial spaced relationship;

means sealing the circular space between said first and second members to define an evacuated housing;

a pair of ring contacts in the form of incomplete circles supported in spaced parallel relationship within said housing;

a pair of relatively movable contact rods extending into said housing in sealed relationship therewith, each of said contact rods being connected to one end of an associated ring contact; and,

restricting means within said housing and disposed on each side of said ring contacts, said restricting means being operable to effect lateral repression of an are moving between said ring contacts to prevent the sidewise looping of the arc.

8. A vacuum circuit interrupter according to claim 7 wherein said first and second circular members are metallic, and said first circular member is provided with an axial bore the axis of which coincides with the axis of said second member; and,

said restricting means being formed as a part of the outer peripheral surface of said first member and the inner peripheral surface of said second member.

9. A vacuum circuit interrupter according to claim 8 wherein said outer peripheral surface of said first member and the inner peripheral surface of said second member also function as a shield which permits heat exchange by direct cooling to the atmosphere circulating around said interrupter.

10. A vacuum circuit interrupter according to claim 9 wherein said first and second members are constructed of a vacuum tight insulating material.

11. A vacuum circuit interrupter according to claim 9 wherein said outer peripheral surface of said first member and said inner peripheral surface of said second member are formed in a manner that in crosssection they present an hour glass configuration having an upper and lower chamber separated by a restrictive portion; and,

said ring contacts are disposed-in the space between said first and second member at the restrictive portion thereof.

12. A vacuum circuit interrupter according to claim 11 wherein said sealing means for sealing the space between said first and second members are metallic plates each having an axial opening the diameter of which is equal to the diameter of the bore of said first member;

a first hollow insulator extending through one of said metallic plates into the evacuated space between said first and second member, one of said contact rods extending through said first insulator in sealed relationship thereto and into connected engagement with one end of one said ring contacts;

second hollow insulator extending through the other of said metallic plates into the evacuated space between said first and second members, the other of said contact rods extending through said second insulator in sealed relationship thereto and for limited axial movement, said other contact rod being connected to one end of the other of said ring contacts;

whereby axial movement of the one contact rod in a first direction will deflect the end of the ring contact to which it is connected to a contact closed position into engagement with said other ring contact, and axial movement of said one contact rod in the opposite direction will move the end of the ring contact to which the said one contact rod is connected to a contact open position out of engagement with said other ring contact.

13. In a vacuum circuit interrupter,

a first hollow circular member having open ends;

a second hollow circular member having open ends and concentrically disposed within said first member to define a circular space between said first and second members;

a first circular end plate secured to the axial end faces of said first and second members at one end thereof, said first circular plate having an axial opening, said first and second members and said end plates cooperating to define an evacuated circular space;

a pair of ring contacts in the form of incomplete circles supported in spaced apart relationship within the evacuated circular space;

a pair of separable contact rods extending into the evacuated circular space, one of said contact rods being connected to one end of one of said ring contacts and the other of said contact rods being connected to one end of the other of said ring contacts;

a first set of circular ring discs comprising a plurality of stacked discs arranged in coaxial spaced apart relationship and disposed around said ring contacts but not in contact therewith;

a second set of circular ring discs comprising a plurality of stacked discs arranged in coaxial spaced apart relationship within said ring contacts but not in contact therewith;

whereby an are moving around said ring contacts is prevented from sidewise looping in either direction by said first and second set of stacked discs and said sets of stacked discs operate as a shield to intercept arc particles and also serve as heat sinks to transfer the heat away from the arc zone.

14. A vacuum circuit interrupter according toclaim 13 wherein saiddiscs in each of said stack of discs are deformed so that a labyrinthpassage betweenadjacent discs in each stack of discs is provided for intercepting arc particles.

15. A vacuum circuit interrupter according to claim 14 wherein said discs in each stack of discs are deformed by means of a circular depression being formed therein.

16. A vacuum circuit interrupter according to claim 14 wherein said first set of stacked discs includes at least one disc having an internal diameter that is less than the internal diameter of the remainder of the discs of said first set, said disc being disposed within said stack midway between the ends thereof;

said second set of stacked discs also including at least one disc having an outer diameter larger than the outer diameters of the remainder of the discs in said stack, said disc being disposed within said stack midway between the ends thereof,

the said discs cooperating to effect a greater repression on the lateral sidewise looping of an arc than the remainder of said discs in each of said stacks of discs.

17. A vacuum interrupter according to claim 1 wherein said restricting means includes a first metallic circular member having an axial bore the diameter of which is sufficiently large enough to permit said first member to encompass said ring contacts in close proximity thereto but not in contact therewith;

a second metallic circular member having a diameter which is less than the internal diameter of said ring contacts wherein said second member is disposed within said ring contacts in close proximity thereto but not in contact therewith;

said first and second member being operable to effect lateral repression of an are moving between said ring contacts to prevent sidewise looping of the arc and said first and second member also serves as a shield having high heat absorbing capacity.

18. A vacuum circuit interrupter according to claim 17 wherein the wall surface of the bore of said first member is provided with a plurality of axially spaced circular grooves; and,

wherein the peripheral surface of said second member is provided with a plurality of axially spaced circular grooves;

said grooves of said-first and second members cooperating to provide a shield which surrounds said ring contacts to effectively intercept arc particles and having a relatively high heat absorbing capacity.

19. A vacuum circuit interrupter according to claim 18 wherein said second member is suspended within said housing in insulated relationship thereto; and,

said first member is supported in operative cooperating position adjacent to said ring contacts and in floating relationship to said housing by said first member.

20. A vacuum circuit interrupter according to claim 19 wherein said first member and said second member are metallically interconnected to provide a massive shield structure having high heat absorbing capacity and presenting a relatively large shield area in a relatively small volume.

21. A vacuum circuit interrupter according to claim 19 wherein said housing includes an insulated circular body and having metallic end caps constructed and arranged to provide a highly evacuated envelope;

and said pair of relatively movable contact rods extending into said envelope through said end caps;

means extending inwardly from the inner surfaces of said end caps for supporting said ring contacts in suspended spaced apart relationship within said envelope;

a first insulator attached to one of said end caps and operatively connected to said second member;

a second insulator attached to the other of said end caps and operatively connected to said second member; and,

metallic support means interconnecting said first and second member together in operative relationship;

whereby said first and second insulator operate to support said first and second members in suspended relationship within said envelope in position to encompass said ring contacts.

22. In a vacuum circuit interrupter;

an evacuated housing;

a stationary contact rod extending into said housing in sealed relationship thereto;

a first ring contact rigidly mounted in said housing in the form of an incomplete toroid and having one end connected to said stationary contact rod, said first ring contact lying in a plane which is transverse to the axis of said stationary contact rod;

an axially movable contact rod extending into said evacuated housing in substantially axial alignment with said stationary contact rod;

a second ring contact in the fonn of an incomplete toroid and having one end connected to said movable contact rod, said second ring contact lying in a plane which is transverse to the axis of said movable contact rod, said first and second ring contacts being in substantial registry, and said second ring contact being deformable to permit engagement of the ends of said ring contacts to which the contact rods are connected;

first tubular constrictive means surrounding said first and second ring contacts in spaced relation thereto; and

second tubular constrictive means inside but spaced from said first and second ring contacts, said first and second tubular constrictive means cooperating to define a constricting passage to prevent sideways looping of the are drawn between said first and second ring contact.

23. In a vacuum circuit interrupter;

an evacuated housing;

relatively movable axially aligned contact rods extending into said housing in sealed relationship therewith;

a pair of spaced apart ring contacts disposed in said housing and arranged in coaxial relationship, each ring contact having the form of an interrupted toroid and each having one end connected to the end of an associated contact rod, said ring contacts when in contact open position lying in substantially parallel planes which are transverse to the axes of said contact rods, at least a portion of at least one of said ring contacts being relatively movable with respect to the other ring contact in response to relative movement of said contact rods; and,

constricting means spaced from but surrounding said ring contacts to inhibit looping of an arc established between said ring contacts when said contacts are moved to contact open position.

24. An interrupter according to claim 23 including magnetic means disposed concentrically of at least one of said ring contacts for producing a radiating magnetic field.

25. In a vacuum circuit interrupter;

an evacuated housing;

a pair of relatively movable contact rods extending into said housing in coaxial relationship;

a first ring contact supported within said housing,

said first ring contact being in the form of an incomplete circle and having one end electrically and mechanically connected to one of said contact rods;

a second ring contact supported within said housing in coaxial spaced parallel relationship to said first ring contact, said second ring contact being in the form of an incomplete circle having one end thereof electrically and mechanically connected to the other one of said contact rods;

shield means surrounding each of said ring contacts and cooperating to restrict the arc drawn between the ring contacts to reduce sideway motion of the arc column in a direction transverse to the longitudinal direction of the ring contacts so that the arc is free to move only along the ring contacts.

26. A vacuum circuit interrupter according to claim 25 wherein said shield means surrounding each ring contact is metallic and is exposed externally to atmosphere without impairing the vacuum within said housmg.

27. A vacuum circuit switch according to claim 26 wherein said shield means is constructed and arranged to have considerable mass to increase the heat absorbing capacity of said shield.

28. A vacuum circuit switch according to claim 26 wherein said shield presents a shield area opposite the length of the ring contacts over which the arc passes and extending one centimeter in either direction of the arc between said ring contacts. 

1. In a vacuum circuit interrupter; an evacuated housing; a pair of ring contacts in the form of incomplete toroids supported within said housing; a pair of relatively movable contact rods extending into said housing with each contact rod being connected to an end of an associated ring contact; and, restricting means supported in insulated relationship within said housing and operable on an arc moving between said ring contacts to effect lateral repression of an arc to prevent sidewise looping of the arc.
 2. A vacuum circuit interrupter according to claim 1 wherein said restricting means operates from both sides of said ring contacts on an arc moving between said ring contacts.
 3. A vacuum circuit interrupter according to claim 2 wherein said restricting means also serves as a shield to intercept metallic arc particles which are developed when an arc is drawn between said ring contacts.
 4. A vacuum circuit interrupter according to claim 3 wherein said ring contacts are supported in spaced parallel relationship and one end of one of said ring contacts is deflectable into and out of engagement with adjacent end of the other of said ring contacts.
 5. A vacuum circuit interrupter according to claim 4 wherein said shield presents a shield area opposite the length of said ring contacts over which the arc passes and extending approximately one centimeter in either direction of the arc length between said ring contacts.
 6. A vacuum circuit interrupter according to claim 1 wherein there is provided means for enhancing the self magnetic field of an arc moving around said ring contacts to thereby increase the speed of the arc along said ring contacts.
 7. In a vacuum circuit interrupter; a first circular member; a second circular member surrounding said first circular member in radial spaced relationship; means sealing the circular space between said first and second members to define an evacuated housing; a pair of ring contacts in the form of incomplete circles supported in spaced parallel relationship within said housing; a pair of relatively movable contact rods extending into said housing in sealed relationship therewith, each of said contact rods being connected to one end of an associated ring contact; and, restricting means within said housing and diSposed on each side of said ring contacts, said restricting means being operable to effect lateral repression of an arc moving between said ring contacts to prevent the sidewise looping of the arc.
 8. A vacuum circuit interrupter according to claim 7 wherein said first and second circular members are metallic, and said first circular member is provided with an axial bore the axis of which coincides with the axis of said second member; and, said restricting means being formed as a part of the outer peripheral surface of said first member and the inner peripheral surface of said second member.
 9. A vacuum circuit interrupter according to claim 8 wherein said outer peripheral surface of said first member and the inner peripheral surface of said second member also function as a shield which permits heat exchange by direct cooling to the atmosphere circulating around said interrupter.
 10. A vacuum circuit interrupter according to claim 9 wherein said first and second members are constructed of a vacuum tight insulating material.
 11. A vacuum circuit interrupter according to claim 9 wherein said outer peripheral surface of said first member and said inner peripheral surface of said second member are formed in a manner that in cross-section they present an hour glass configuration having an upper and lower chamber separated by a restrictive portion; and, said ring contacts are disposed in the space between said first and second member at the restrictive portion thereof.
 12. A vacuum circuit interrupter according to claim 11 wherein said sealing means for sealing the space between said first and second members are metallic plates each having an axial opening the diameter of which is equal to the diameter of the bore of said first member; a first hollow insulator extending through one of said metallic plates into the evacuated space between said first and second member, one of said contact rods extending through said first insulator in sealed relationship thereto and into connected engagement with one end of one said ring contacts; a second hollow insulator extending through the other of said metallic plates into the evacuated space between said first and second members, the other of said contact rods extending through said second insulator in sealed relationship thereto and for limited axial movement, said other contact rod being connected to one end of the other of said ring contacts; whereby axial movement of the one contact rod in a first direction will deflect the end of the ring contact to which it is connected to a contact closed position into engagement with said other ring contact, and axial movement of said one contact rod in the opposite direction will move the end of the ring contact to which the said one contact rod is connected to a contact open position out of engagement with said other ring contact.
 13. In a vacuum circuit interrupter, a first hollow circular member having open ends; a second hollow circular member having open ends and concentrically disposed within said first member to define a circular space between said first and second members; a first circular end plate secured to the axial end faces of said first and second members at one end thereof, said first circular plate having an axial opening, said first and second members and said end plates cooperating to define an evacuated circular space; a pair of ring contacts in the form of incomplete circles supported in spaced apart relationship within the evacuated circular space; a pair of separable contact rods extending into the evacuated circular space, one of said contact rods being connected to one end of one of said ring contacts and the other of said contact rods being connected to one end of the other of said ring contacts; a first set of circular ring discs comprising a plurality of stacked discs arranged in coaxial spaced apart relationship and disposed around said ring contacts but not in contact therewith; a second set of circular ring discs comprising a plurality of stacked discs arranged in coaxial spaced apart relationship within said ring contacts but not in contact therewith; whereby an arc moving around said ring contacts is prevented from sidewise looping in either direction by said first and second set of stacked discs and said sets of stacked discs operate as a shield to intercept arc particles and also serve as heat sinks to transfer the heat away from the arc zone.
 14. A vacuum circuit interrupter according to claim 13 wherein said discs in each of said stack of discs are deformed so that a labyrinth passage between adjacent discs in each stack of discs is provided for intercepting arc particles.
 15. A vacuum circuit interrupter according to claim 14 wherein said discs in each stack of discs are deformed by means of a circular depression being formed therein.
 16. A vacuum circuit interrupter according to claim 14 wherein said first set of stacked discs includes at least one disc having an internal diameter that is less than the internal diameter of the remainder of the discs of said first set, said disc being disposed within said stack midway between the ends thereof; said second set of stacked discs also including at least one disc having an outer diameter larger than the outer diameters of the remainder of the discs in said stack, said disc being disposed within said stack midway between the ends thereof, the said discs cooperating to effect a greater repression on the lateral sidewise looping of an arc than the remainder of said discs in each of said stacks of discs.
 17. A vacuum interrupter according to claim 1 wherein said restricting means includes a first metallic circular member having an axial bore the diameter of which is sufficiently large enough to permit said first member to encompass said ring contacts in close proximity thereto but not in contact therewith; a second metallic circular member having a diameter which is less than the internal diameter of said ring contacts wherein said second member is disposed within said ring contacts in close proximity thereto but not in contact therewith; said first and second member being operable to effect lateral repression of an arc moving between said ring contacts to prevent sidewise looping of the arc and said first and second member also serves as a shield having high heat absorbing capacity.
 18. A vacuum circuit interrupter according to claim 17 wherein the wall surface of the bore of said first member is provided with a plurality of axially spaced circular grooves; and, wherein the peripheral surface of said second member is provided with a plurality of axially spaced circular grooves; said grooves of said first and second members cooperating to provide a shield which surrounds said ring contacts to effectively intercept arc particles and having a relatively high heat absorbing capacity.
 19. A vacuum circuit interrupter according to claim 18 wherein said second member is suspended within said housing in insulated relationship thereto; and, said first member is supported in operative cooperating position adjacent to said ring contacts and in floating relationship to said housing by said first member.
 20. A vacuum circuit interrupter according to claim 19 wherein said first member and said second member are metallically interconnected to provide a massive shield structure having high heat absorbing capacity and presenting a relatively large shield area in a relatively small volume.
 21. A vacuum circuit interrupter according to claim 19 wherein said housing includes an insulated circular body and having metallic end caps constructed and arranged to provide a highly evacuated envelope; and said pair of relatively movable contact rods extending into said envelope through said end caps; means extending inwardly from the inner surfaces of said end caps for supporting said ring contacts in suspended spaced apart relationship within said envelope; a first insuLator attached to one of said end caps and operatively connected to said second member; a second insulator attached to the other of said end caps and operatively connected to said second member; and, metallic support means interconnecting said first and second member together in operative relationship; whereby said first and second insulator operate to support said first and second members in suspended relationship within said envelope in position to encompass said ring contacts.
 22. In a vacuum circuit interrupter; an evacuated housing; a stationary contact rod extending into said housing in sealed relationship thereto; a first ring contact rigidly mounted in said housing in the form of an incomplete toroid and having one end connected to said stationary contact rod, said first ring contact lying in a plane which is transverse to the axis of said stationary contact rod; an axially movable contact rod extending into said evacuated housing in substantially axial alignment with said stationary contact rod; a second ring contact in the form of an incomplete toroid and having one end connected to said movable contact rod, said second ring contact lying in a plane which is transverse to the axis of said movable contact rod, said first and second ring contacts being in substantial registry, and said second ring contact being deformable to permit engagement of the ends of said ring contacts to which the contact rods are connected; first tubular constrictive means surrounding said first and second ring contacts in spaced relation thereto; and second tubular constrictive means inside but spaced from said first and second ring contacts, said first and second tubular constrictive means cooperating to define a constricting passage to prevent sideways looping of the arc drawn between said first and second ring contact.
 23. In a vacuum circuit interrupter; an evacuated housing; relatively movable axially aligned contact rods extending into said housing in sealed relationship therewith; a pair of spaced apart ring contacts disposed in said housing and arranged in coaxial relationship, each ring contact having the form of an interrupted toroid and each having one end connected to the end of an associated contact rod, said ring contacts when in contact open position lying in substantially parallel planes which are transverse to the axes of said contact rods, at least a portion of at least one of said ring contacts being relatively movable with respect to the other ring contact in response to relative movement of said contact rods; and, constricting means spaced from but surrounding said ring contacts to inhibit looping of an arc established between said ring contacts when said contacts are moved to contact open position.
 24. An interrupter according to claim 23 including magnetic means disposed concentrically of at least one of said ring contacts for producing a radiating magnetic field.
 25. In a vacuum circuit interrupter; an evacuated housing; a pair of relatively movable contact rods extending into said housing in coaxial relationship; a first ring contact supported within said housing, said first ring contact being in the form of an incomplete circle and having one end electrically and mechanically connected to one of said contact rods; a second ring contact supported within said housing in coaxial spaced parallel relationship to said first ring contact, said second ring contact being in the form of an incomplete circle having one end thereof electrically and mechanically connected to the other one of said contact rods; shield means surrounding each of said ring contacts and cooperating to restrict the arc drawn between the ring contacts to reduce sideway motion of the arc column in a direction transverse to the longitudinal direction of the ring contacts so that the arc is free to move only along the ring contacts.
 26. A vacuum circuit interrupter according to claim 25 whErein said shield means surrounding each ring contact is metallic and is exposed externally to atmosphere without impairing the vacuum within said housing.
 27. A vacuum circuit switch according to claim 26 wherein said shield means is constructed and arranged to have considerable mass to increase the heat absorbing capacity of said shield.
 28. A vacuum circuit switch according to claim 26 wherein said shield presents a shield area opposite the length of the ring contacts over which the arc passes and extending one centimeter in either direction of the arc between said ring contacts. 